The invention relates to a plant for producing semiconductor products.
Plants of this type can be constructed in particular as a plant for processing wafers. These plants contain a large number of production units, with which different production processes can be carried out. The production processes are, in particular, etching processes, wet chemical methods, diffusion processes and different cleaning processes, such as a chemical mechanical polishing (CMP) process. For each of the processes, one or more production units are provided, in which various production steps in a production process are carried out.
In addition, plants of this type contain a large number of measuring units. In the measuring units, the quality of processing of one or more production steps in a production process is checked.
The entire production process is subject to strict cleanness requirements, so that the production units and the measuring units are disposed in a clean room or in a system of clean rooms.
The wafers are supplied to the individual production units by a transport system, in predetermined batch sizes in cassettes. In addition, the outward transport of the cassettes following the processing of the wafers is carried out by the transport system.
The transport system typically has a conveyor system that, for example, is constructed in the form of roller conveyors. Here, the cassettes with the wafers are transported lying on the roller conveyors. Alternatively, the conveyor system can also contain continuous conveyors, suspension conveyors or the like.
Such conveyor systems run linearly through the clean room. In order to ensure the supply of the cassettes with the wafers to the production units, the conveyor systems branch in a suitable way. In this way, a more or less self-contained network of roller conveyors is produced within the clean room.
In order to ensure an adequate supply of wafers to the production units and the measuring units, the transport system additionally has a storage system, which has a specific number of storage units that are distributed suitably over the clean room. Storage units of this type are typically constructed as stockers, which are attached to the conveyor system. Temporarily stored in the stockers in each case is a predefined number of cassettes with wafers. The cassettes with wafers are removed from the stockers in a suitable number as required and, via the conveyor system, are supplied to the production units and the measuring units.
The disadvantage in this case, however, is that storing the cassettes with wafers in the stockers is very time-consuming and costly.
In the publication titled xe2x80x9cWhat Gain from Small Batch Manufacturingxe2x80x9d, by George Horn and William A. Podgorski in xe2x80x9cSemiconductor Fabtechxe2x80x9d, 8th Edition, a plant structure is proposed with which the number of stockers can be reduced.
The transport system described there contains, in addition to a conveyor system, a plurality of local process buffers. In this case, a process buffer is in each case assigned to a plurality of identical production units that in each case process the same production steps in a production process. In addition, storage units with larger storage capacities are provided for a plurality of production units and measuring units supplementing a production process, if corresponding storage capacities are required for such production processes. The production processes include, for example, diffusion processes.
Although, in a plant of this type, stockers are no longer needed, the expenditure of time for storing the cassettes with wafers and removing them again is still considerable. Depending on the processing capacities of the production unit and measuring units, cassettes have to be stored temporarily in a sufficient number in the local process buffers and in the storage units that are used to supply the production units and measuring units of a production process. The cassettes have to be removed from the storage unit again and assigned to the respective production units and measuring units, in order that they can be supplied to the production units and the measuring units via the conveyor system.
It is accordingly an object of the invention to provide a plant for producing semiconductor products which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which provides the simplest, most efficient and cost-effective supply of semiconductor products possible to the individual production and measuring units.
With the foregoing and other objects in view there is provided, in accordance with the invention, a plant for producing semiconductor products such as wafers. The plant includes at least one clean room and a plurality of processing stations disposed in the clean room. Each of the processing stations contains at least one unit selected from the group consisting of production units and measuring units, and a production buffer for storing the semiconductor products. The production buffer is disposed directly at the unit. Each of the processing stations also has a handling device for automatic delivery and outward transport of the semiconductor products to and from the production buffer. A conveyor system interconnects the processing stations.
The plant according to the invention has the configuration of processing stations. Each of the processing stations has at least one production or measuring unit and also a production buffer, disposed on the latter, for the storage of semiconductor products. Also provided is a handling device, which is likewise a constituent part of the processing station. By the handling device, the delivery of the semiconductor products to the production buffer, and the outward transport of the products from the buffer are respectively carried out automatically.
The individual processing stations are interconnected via a conveyor system, via which the semiconductor products are transported between the individual processing stations.
The significant advantage of the plant according to the invention is that the semiconductor products are delivered to production buffers that are disposed directly at the production or the measuring units. From the production buffers, the semiconductor products can therefore be fed directly into the production or measuring units, without any further removal from the storage unit and supply via further transport devices being necessary. Saving transport devices of this type leads to a significant saving in costs. It is particularly advantageous here that, in the process station, no storage systems such as stockers or local process buffers are provided, from which temporarily stored semiconductor products have to be removed, sorted out and supplied to the various production or measuring units. Instead, the semiconductor products on the production buffers can already be assigned to the respective production or measuring units.
Storing the semiconductor products in the production buffers therefore leads to a considerable saving in costs and to simplification of the material flow in the plant, as a result of omitting stockers and local process buffers.
A further advantage can be seen in the fact that the production buffers can be attached directly to the production or measuring units, in a space-saving way, which leads to a low requirement for space for the plant.
Finally, it is advantageous that the transport of the semiconductor products within a processing station can be carried out very quickly and without the use of any personnel. The handling device, which can be constructed in particular as a robot or rack server, automatically supplies the semiconductor products delivered by the conveyor system to the production buffers and also ensures that they are transported away to the conveyor system. In addition, the removal of semiconductor products from a production buffer, subsequent insertion into the production or measuring unit and the subsequent removal are preferably carried out automatically by robots, grippers or the like.
In a particularly advantageous embodiment, the production buffers are constructed in the form of storage racks. Storage racks of this type are cost-effective and, in addition, can be populated with semiconductor products simply and rapidly by the rack server. The storage racks are particularly advantageously disposed immediately in front of or above loading and unloading stations on the respective production or measuring units.
Therefore, not only that an extremely space-saving installation of the production buffer on the respective production or measuring unit is provided, but also that the production buffers are disposed in the immediate vicinity of the loading and unloading station which is used to supply the semiconductor products to the respective production unit and measuring unit. By this configuration, the expenditure on the transport of the semiconductor products between the loading and unloading stations and the storage rack is reduced to a minimum.
Finally, the capacities of the storage racks can advantageously be matched in a straightforward way to the requirement for semiconductor products, by a suitable selection of the size of the storage racks. It is, moreover, advantageous that the semiconductor products can be supplied to the individual storage racks on the Kanban principle. If the filling level of a storage rack falls below a predefined desired value, the storage rack is repopulated with a predefined number of semiconductor products by the rack server.
In accordance with an added feature of the invention, the handling device is a rack server.
In accordance with an additional feature of the invention, the rack server has at least two set-down surfaces. It being possible for the cassettes with the semiconductor products to be supplied to the production buffer to be set down on a first of the set-down surfaces and for the cassettes with the semiconductor products for outward transport from the unit to be set down on a second of the set-down surfaces.
In accordance with another feature of the invention, the rack server has grippers with which the cassettes with the semiconductor products can be supplied to the production buffer and removed from the production buffer.
In accordance with a further feature of the invention, drive-to positions of the unit of a respective one of the processing stations are stored as parameter values in the rack server belonging to the respective processing station.
In accordance with another added feature of the invention, a plurality of the production units and the measuring units for carrying out a production process are disposed in a respective one of the processing stations.
In accordance with another additional feature of the invention, the production units and the measuring units are each formed of at least device selected from the group consisting of machines and staff workplaces.
In accordance with another further feature of the invention, the production buffer has a level control for determining a quantity of semiconductor products stored in the production buffer. The production buffer is refilled as soon as a filling level of the production buffer falls below a predefined desired value.
In accordance with a further added feature of the invention, at least one further production buffer is provided and functions as a transfer station for the semiconductor products for a bi-directional exchange of the semiconductor products with the conveyor system.
In accordance with a concomitant feature of the invention, the further production buffer forming the transfer station has a storage rack with a predefined number of rack compartments. The rack compartments are accessible to the handling device of the processing stations and via the transfer station the semiconductor products are transported from and to the conveyor system.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a plant for producing semiconductor products, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.